1. Field of the Invention
The present invention relates to a liquid crystal display device and, more particularly, to a stereoscopic liquid crystal display device having a touch panel and a method for manufacturing the same, wherein a stable touch detection can be performed without influencing the operation of a neighboring display panel or an electrically-driven liquid crystal lens.
2. Discussion of the Related Art
Recently, as the world has reached a full-scale information age, the field of display that can visually express electric information signals has developed at a vast rate. And, in order to meet with the requirements of such development, various types of flat display devices having excellent functions and characteristics, such as compact size, light weight, low power consumption rate, and so on, have been developed so replace the cathode ray tube (CRT) displays.
Detailed examples of such flat display devices may include liquid crystal display (LCD) devices, plasma display panel (PDP) devices, field emission display (FED) devices, electro-luminescence display (ELD) devices, and so on. More specifically, these flat display devices commonly include a flat display panel realizing images as an essential element. Herein, a flat display device has the structure of a pair of transparent insulation layers bonded so as to face into each other between unique light-emitting or polarization material layers.
Herein, the liquid crystal display device uses an electric field to adjust light transmissivity of the liquid crystals, thereby display an image. In order to do so, an image display device consists of a display panel having liquid crystal cells, and a driving circuit for driving a backlight unit and the liquid crystal cells, wherein the backlight unit emits light rays to the display panel.
The display panel is configured so that a plurality of gate lines and a plurality of data lines crossover one another, so as to define a plurality of unit pixel regions. At this point, each pixel region is provided with a thin film transistor array substrate and a color filter array substrate facing into each other, a spacer maintaining a predetermined cell gap between the thin film transistor array substrate and the color filter array substrate, and liquid crystal filling the cell gap.
A thin film transistor array substrate consists of gate lines and data lines, a thin film transistor formed as a switching device at each crossing point between the gate lines and the data lines, pixel electrodes formed in liquid crystal cell units and connected to the thin film transistor, and an alignment layer deposited thereon. Each of the gate lines and the data lines receives a signal from driving circuits through a pad unit.
The thin film transistor responds to a scan signal supplied to the gate line, so as to a supply pixel voltage signal, which is supplied to the data line, to the pixel electrode.
The color filter array substrate consists of color filters formed in liquid crystal cell units, a black matrix for identifying the color filters and for reflecting external light, common electrodes commonly supplying reference voltage to the liquid crystal cells, and an alignment layer deposited thereon.
Thereafter, the thin film transistor array substrate and the color filter array substrate that are separately configured, as described above, are aligned and bonded so as to face into each other. Subsequently, liquid crystal is injected between the two substrates, which are then sealed.
Recently, demands for adding a touch panel to the liquid crystal display device having the above-described structure have been increasing. Herein, the touch panel may recognize specific portions touched by the hand of the user or by a separate input means and may transmit separate information with respect to recognized portion of the screen (or panel).
Additionally, apart from the touch panel, the liquid crystal display device is also separately provided with a lenticular lens for displaying stereoscopic images.
Hereinafter, the related art stereoscopic liquid crystal display device having a touch panel fixed thereto will now be described in detail with reference to the accompanying drawings.
FIG. 1 illustrates a cross-sectional view showing a liquid crystal display device having a general touch panel fixed thereto.
Referring to FIG. 1, the liquid crystal display device having a general touch panel fixed thereto is sequentially provided with a liquid crystal panel 1, and a touch panel layer 50. The liquid crystal display device is also provided with an adhesion layer 45 between the interface.
Herein, the adhesion layer 45 corresponds to a double-sided adhesion layer adhering (or bonding) the liquid crystal layer panel 1 to the touch panel layer 50.
Also, the liquid crystal panel 1 includes a first substrate 10 and a second substrate 20 facing into each other, a liquid crystal layer 30 filling the space between the first substrate 10 and the second substrate 20, a color filter layer 21 (21a, 21b, and 21c) formed on each surface of the second substrate 20 touching (or contacting) the liquid crystal layer 30, and a common electrode 22 formed on an entire surface of the color filter layer 21. Although it is not shown in the drawing, a first polarizing layer and a second polarizing layer may be further included on each rear surface of the first substrate 10 and the second substrate 20.
Also, the touch panel 50 is separately provided with an adhesion layer 45 on the liquid crystal panel 1, wherein the adhesion layer 45 is placed between the touch panel 50 and the liquid crystal panel 1. Herein, the inner structure may vary in diverse formats depending upon the operation (or driving) method.
For example, the touch panel 50 may be divided into a resistive type and a capacitive type. And, in this case, a patterned transparent electrode is formed inside of the touch panel 50.
Firstly, a resistive touch panel essentially consists of conductive transparent electrodes facing into one another. The gap (or space) between the transparent electrodes facing into one another maintains a predetermined distance by a finely printed spacer, thereby being electrically insulated. When a constant voltage is applied to each transparent electrode, and when the upper substrate is touched by the hand of a user or by a touch-pen, a change in resistance occurs in each of the upper substrate (X-axis) and the lower substrate (Y-axis) in accordance with the touched position. At this point, the resistive touch panel uses a controller to calculate the position of the upper substrate (X-axis) and the lower substrate (Y-axis) where the change in the resistance value has occurred, thereby displaying the corresponding coordinates on the monitor or inputting the data.
The capacitive touch panel is provided with a detection electrode of a transparent electrode component and a signal applying electrode, wherein a change in voltage caused by a fine current flow is sensed at a touched point, thereby detecting whether or not and where a touch has occurred.
Therefore, when the above-described resistive or capacitive touch panel is positioned on the liquid crystal panel, a parasitic capacitance may occur between a transparent electrode within the touch panel and a common electrode of the liquid crystal panel. Such parasitic capacitance may be applied as a noise for sensing a touch.
In order to block (or prevent) such noise, a structure of forming a rear electrode of a transparent electrode component on a rear surface side of the liquid crystal panel has been proposed.
FIG. 2a shows an example of a signal measuring method in a stereoscopic liquid crystal display device having a touch panel. And, FIG. 2b and FIG. 2c illustrates wave forms showing noise generation, in a related art stereoscopic liquid crystal display device having a general touch panel.
FIG. 2a shows an example wherein a rear electrode of a transparent electrode component is formed on a polarizing layer above the liquid crystal panel (not shown) and set to a floating state, and wherein an electrode 62 of the touch panel is then placed above the rear electrode 61.
Herein, a substrate of the touch panel, which functions as an insulating layer, has been omitted in the drawing. Also, the electrode 62 of the touch panel corresponds to an electrode patterned to a predetermined form.
At this point, when measuring a signal generated from the electrode 62 of the touch panel, a section having an bouncing signal value at a specific point occurs even when a touch has not occurred, as shown in FIG. 2b and FIG. 2c. The signals bouncing at a specific point are referred to as noise, and the cause of such bouncing of the signals (or noise) is known as an influence of a gate clock signal being applied to the liquid crystal panel.
Therefore, in a structure fixing a touch panel on a liquid crystal panel provided with a rear electrode, since it is not yet possible to completely and fully prevent a parasitic capacitance or noise caused by the liquid crystal panel from occurring, efforts are being made in order to implement a solution to such problems.
As described above, the related art liquid crystal display device having a touch panel fixed thereto has the following disadvantages.
For example, in case of a capacitive or resistive touch panel, a parasitic capacitance may occur between a transparent electrode provided in the touch panel and a common electrode provided in the liquid crystal panel, and such parasitic capacitance may be recognized as noise, thereby causing a malfunction in the touch detection.
Also, even when a rear electrode is provided on a rear surface side of a liquid crystal panel in order to block (or prevent) any influence caused by the liquid crystal panel, a noise may occur in a specific section even when no touch has occurred. And, in case the touch panel is positioned above the liquid crystal panel, there may be difficulty in that the touch panel cannot fully and completely block (or prevent) influence caused by the liquid crystal panel.
Furthermore, apart from the touch panel on liquid crystal display for realizing 3D display, in case of a display device being separately provided with a lens layer having a lens function for displaying stereoscopic images in order to implement 3D display, a shape-forming process for forming each lens layer and a bonding process for bonding the lens layer having a curved surface are performed. Thus, increasing the fabrication (or manufacturing) cost for forming the display device having complex functions.